Unit dose articles filled with compositions, particularly household care compositions such as laundry detergent, are becoming more popular with consumers. Generally, such articles are made in part by forming compartments in a web, for example, a web of water-soluble film, filling the compartments with a composition, and then sealing and separating the articles. The webs are often disposed on a moving surface, such as on a rotary drum or on a horizontal conveyor belt, and the compartments are filled as they move past filling nozzles. In larger scale manufacturing lines there are typically multiple filling nozzles in a lane in the machine direction MD and multiple lanes in parallel with one another in the cross direction CD. For example, a manufacturer may have twelve lanes, each lane having four nozzles, for a total of forty-eight nozzles. The nozzles are typically crowded closely together to allow more nozzles to fit within compact space. The lanes are typically crowded closely together to allow more lanes to fit within compact space. Having more nozzles allows for an increase in the number of compartments that can be filled simultaneously. Manufacturers are continually looking for ways to increase the speed and efficiency of the process of filling compartments with fluid compositions.
The type of composition being dispensed can provide filling challenges. During manufacture, the time it takes to fill a compartment with a fluid depends a great deal on the rheological properties of the fluid. Higher-viscosity compounds may result in a filament or string that forms and hangs down from the filling nozzle at the end of the filling event, and this filament or string takes some time to break up. The time to break up is typically longer than desired and imposes a limitation to the speed at which consecutive filling events can take place. The time to break up sometimes can be the controlling factor for selecting the maximum speed at which the filling operation can run, as speeding up the filling operation before the filament or string breaks up will cause fluid to fall on the web in between the compartments. Lower-viscosity compounds may splash out of cavities when dispensed quickly which will also cause fluid to fall on the web in between the compartments. Fluid located on the web in between the compartments causes difficulty in sealing and separating the articles.
To compensate for the problem associated with stringing, a valve can be joined to the tip of the filling nozzle that only opens when filling is needed and closes rapidly at the end of the filling event. In a compact filling apparatus, there is little space to install valves next to all of the nozzles. Furthermore, adding valves would also add extra weight to reciprocating shuttles that are often employed to enable continuous web motion. Starting and stopping a heavy shuttle can result in over stressing and fatigue of the driving motor and moving parts. Additionally, having a valve does not always solve the problem because there are physical parts on the exit side of the valve that can become wetted with fluid and can give rise to further stringing and dripping.
In view of the above, there is a continuing unaddressed need for lightweight apparatus and processes that are capable of quickly filling a succession of compartments with minimal stringing and dripping of the fluid and that are capable of cleanly shutting off the flow of fluid to avoid stringing and dripping the fluid outside of the compartments.